title: Two-dimensional ferromagnetism of a 3He film: influence of weak frustration.
abstract: (3)He films adsorbed on the atomically flat surface of graphite provide a model system for the study of two-dimensional magnetism on a triangular lattice. We have made a study of the regime in which the T=0 ground state of the second (3)He layer is a fully polarized ferromagnet. NMR, using broadband SQUID detection, at a range of low fields above the spin-flop transition, and over a wide temperature range 0.3-200 mK, has enabled us to disentangle the influence of sample finite size effects and magnetic field on the spin-wave spectrum. We demonstrate that the spin-wave spectrum is governed by a different effective exchange constant than that determining the high temperature magnetism. This is understood in terms of frustrated atomic ring exchange.
authors.affiliation: Department of Physics, Royal Holloway University of London, Egham, TW20 0EX Surrey, United Kingdom.
authors.forename: A
authors.initials: A
authors.lastname: Casey
authors.forename: M
authors.initials: M
authors.lastname: Neumann
authors.forename: B
authors.initials: B
authors.lastname: Cowan
authors.forename: J
authors.initials: J
authors.lastname: Saunders
authors.forename: N
authors.initials: N
authors.lastname: Shannon